The plan says 54,000 premises will be connected to the NBN using fibre-optic cabling by mid-2013, compared with the original forecast of 137,000. The next federal election will need to be called by October or November.

On ABC Radio, Mr Quigley said his job was to serve the government of the day. But he warned it would require a lot of work and money to change the roll-out technology of the $37.4 billion project.

“If a new government decided to change direction we obviously could finish off contracts,” he said. “You’d keep going on some of it, clearly, and you could then change direction.

“But as you know this is a big and complex technical job to do.

“Changing directions is not simple and would require a lot of engineering, architecture and design work . . . and money.”

Mr Turnbull said that changing policies would be relatively simple. A Coalition government would deliver high-speed broadband faster than Labor’s plan by using a slower and cheaper technology known as fibre to the node that does not connect cables directly to homes.

“No, I don’t [agree with Mr Quigley],” Mr Turnbull told an American Chamber of Commerce event in Sydney on Friday. “I think Mr Quigley probably has become a little bit too much of a political advocate for this project.

“There are plenty of networks in the world that have a mixture of fibre to the premises and fibre to the node and he knows that.

“And, frankly, Telstra and Optus have already done all the engineering work on a fibre to the node deployment in Australia.

“There are plenty of engineering and consulting groups around Australia that know what you need to do and, again, it’s not rocket science.”

Mr Turnbull said a Coalition government would keep its cheaper version of the network in public hands because private companies would not be interested in buying the wholesale network.

“I think it’d be better off not belonging to the Government,” he said. “But I just think it’s going to be very hard practically, and I used to sell businesses and assets for a living, it’d be very hard to sell for quite a long time.

“If you wanted to recover some real value for it you’d have to get it up and running and demonstrating some substantial positive cash flow.”